You only get 2 HQ choices. However, nothing is stopping you from taking both an SHP and a Chaplain, or even two chaplains (see blow)
However, you'll most likely end up with a death company regardless of whether or not you get a chaplain. It's just going to be smaller and, without a chaplain or SHP, it's going to be out of ocntrol (moces and charges after the closest enemy)
SHP is NOT more 'characterful' than a captain, no more than a standard marine army beign led by a chaplain is uncharacterful. The SHP is a religious and inspirational leader to the blood angels, and they;d follow their priests into hell.
The SHP is a decent choice, but best reserved for attaching to high cost squads. Terminators, assault marines, etc where his healing ability will start making up for its point cost.
It's aways a good idea to take at least one chaplain (you can have two and they each get a d3+3 death company, plus the ones recruted from the squads. THey all form one big unit), give him and the DC jetpacks, plan on at least ten to twelve models if you run a lot of squads. Another five or six if you take a second chaplain.
Plan on 5 or 6 per chaplain, + 0.6 for every squad (meaning if you have a total of 5 squads that DC can be recruited from, prepare at least 3 minis in addition to the ones for your chaplain)
I have five squads in my army (2 scouts, 2 tactical, 1 assault), and one chaplain and I pack ten death company (Plus 2 with powerfists, in case they draw from a squad with a vet I feel like giving up) 6 for the chaplain, plus 3 or 4 for inductees. Usually my death copany ends up beign between 8 and 12 men. Usually around 10
For the second HQ slot (usually best to hold bakc on the second HQ except in games with more than 1500 points, just because our chaplains cost so much), SHP and Librarian are both good choices. I like to take a librarian wth a jump pack, fury and fear. I usually have him escoreted by (but not joined up to) an assaut squad so they can move him in close aqnd position him for optimum use of his powers. But against some armies (chaos, eldar)
Save the captain for games where you're running a lot of shooty squads (devistators, las/plas squads, etc), you'll need the LD for target priority. Otherwise, buy vets for any squad that's going into assault. A Powerfist vet is 30 points and more than worth it for assualt squads and assaulty scouts (2 points cheaper for scouts). Dev squads and shooty tac squads, you cn just pop 15 and buy them a naked vet. Get the leadership bonus for target priority and moralle and if you want you can give him up to the DC and get another powerfist in your deathco.
One thing I suggest to all new players is to go to the GW website, hit up their errata and FAQ vault and download the latest FAQs for the main book, the space marines codex, AND (most importantly) the Blood Angels Codex. Read them print them, read them some more.
Also (not to steal thunder from the guys here) but Bolter and Chainsword
has a big and busy Blood Angels section packed with experienced BA players who'll let you know what works best for them.